The Radiation Therapy Oncology Group was founded in January 1971 with the purpose of constituting a group of clinical radiation therapy investigative centers for the purpose of conducting clinical trials and other studies to improve the management of patients with cancer. Funding was via the Clinical Investigation Branch of the National Cancer Institute and the University of Washington was one of the 19 founding members. As of January 1975, there were 26 full member institutions and 13 provisional member institutions. Through the collaboration of these radiotherapy centers, it will be possible to provide an adequate number of patients to answer significant questions in the treatment of cancer not possible on the basis of the number of patients seen in any one institution. Ongoing protocols include studies involving the use of split-course irradiation, brain irradiation for intracranial metastases, hyperbaric oxygen and the radiotherapy of carcinoma of the cervix, carbogen, preoperative irradiation of adenocarcinoma of the rectum, the use of irradiation in head and neck cancer, two lung cancer protocols involving irradiation and chemotherapy in some cases, the use of irradiation in the treatment of osseous metastases and in the treatment of gliomas. Operations headquarters is centered at Thomas Jefferson University Hospital in Philadelphia, Pa., and a sophisticated biostatistical center is functioning as an integral part of the Radiation Therapy Oncology Group, insuring satisfactory methodology of the studies and aiding in establishing an order of priorities for those studies which are of the greatest immediate importance and which can yield an answer in a reasonable period of time.